APC and acute respiratory distress syndrome: In present animal study, our data demonstrated SN50 effectively down-regulated TF and PAI-1 expressions in lung tissue, decreased concentrations of procoagulants (TF, PAI-1, TAT) and promoted activated protein C (APC) in BALF, and attenuated collagen III expression in pulmonary tissue, suggesting that SN50 is expected to be an effective target to attenuate hypercoagulation and fibrinolysis inhibition in ARDS.